i just had Leupold put an M1 elevation turret on. zero at 100, and shoot to 500 or so. record the bullet drop. then plug your bullet and estimated velocity into JBM Ballistics and tweak velocity until it matches your true bullet drop. then print a range card and tape it to your stock (and carry a spare in your pack). This system is not as slick as a BDC retical or knob, but it allows you to change bullets and/or velocity with nothing more than a trip to the shooting range and a new range card from JBM

my 7mm-08 is the lower rifle in this pic.

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Guns don't kill people, drivers with cell phones kill people.